1. Field of the Invention
This disclosure relates to a liquid ejection head configured to eject a liquid, and a liquid ejection apparatus provided with the liquid ejection head. This disclosure also relates to a method of manufacturing the liquid ejection head.
2. Description of the Related Art
A liquid ejection head forms an image by ejecting liquid drops. Ejection of the liquid drops is achieved by heating liquid with an energy generating element provided with a heat generating resistance member and causing the liquid to undergo film boiling. Alternatively, there is a case where a piezoelectric element is used for ejection of the liquid drops, and there is also a case where a method of irradiating the liquid with an electromagnetic wave generated by a laser or the like is used. The liquid ejection head is mounted generally on a recording apparatus body. The liquid ejection head is controlled and driven by an electric signal supplied from the recording apparatus body, and forms an image. Therefore, in order to form an image with the liquid ejection head, electrical communication between the recording apparatus body and the liquid ejection head is required.
In order to realize the electrical communication, the liquid ejection head includes an electric wiring substrate that electrically connects the energy generating element and the recording apparatus body. The electric wiring substrate includes an electric signal input portion including a conductive contact pad, and the recording apparatus body includes a contact pin configured to be electrically connected to the contact pad. Contact between the contact pad and the contact pin enables the electrical communication. As disclosed in Japanese Patent Laid-Open No. 2007-320229, the electric wiring substrate is a flexible wiring substrate having a plurality of electric wiring lines arranged in a single layer, and the contact pad is provided directly on the flexible wiring substrate. In order to reduce the size of the electric signal input portion, there is also a case where a multilayer wiring substrate having a plurality of electric wiring lines arranged in multiple layers is connected to the flexible wiring substrate, and the contact pad is formed on the multilayer wiring substrate. In a manufacturing step of the liquid ejection head, the electric wiring substrate is bent along two surfaces of a housing of the liquid ejection head, and crimped at points the circumference of the electric signal input portion (at four points, for example).
Although a principal portion of the electric wiring substrate, specifically, a bent portion is formed of an easy-to-bend material such as that for a flexible wiring substrate, it is difficult to bend completely along the shape of the housing. Therefore, there is a case where floating occurs in the vicinity of the bent portion at the time of bending.
FIG. 11A and FIG. 11B are a side view and a front view of the liquid ejection head disclosed in Japanese Patent Laid-Open No. 2007-320229. In a liquid ejection head 1 disclosed in Japanese Patent Laid-Open No. 2007-320229, a housing 2 includes a first surface 2a positioned on the same side as an ejection port, a second surface 2b intersecting the first surface 2a, and a corner portion 2c formed by the first and second surfaces 2a and 2b intersecting each other.
An electric wiring substrate 3 includes a first portion 4 supported on the first surface 2a, a second portion 6 including a bent portion 5 bent at the corner portion 2c, and a third portion 7 supported on the second surface 2b. The third portion 7 corresponds to the electric signal input portion described above.
In this manner, when the electric wiring substrate 3 is supported by the housing 2, floating occurs in the vicinity of the bent portion 5 due to the bending rigidity of the electric wiring substrate 3. This tendency is notable in the electric wiring substrate 3 having a large area other than the electric signal input portion and the electric wiring substrate 3 having a large width. The floating of the electric wiring substrate 3 occurs not only at the time of manufacture, but also by heat after usage or a change with time. The floating in the vicinity of the bent portion 5 as described above causes an increase in the dimensions of the liquid ejection head 1, specifically, an increase in a dimension L illustrated in FIG. 11A.
In order to reduce a height of the floating, it is conceivable to fixedly crimp the electric wiring substrate 3 while pulling strongly. However, since the electric wiring substrate 3 is fixed in the state of being applied with a tensile force, a crimped portion of the electric wiring substrate 3 may be cracked, or other portions may wrinkle after the tensile force is released. From these reasons, the electric wiring substrate 3 is preferably supported on the housing 2 in the state of being tensed with an excessive length at the second portion 6, that is, in the state in which the second portion 6 sags.